1. Technical Field
The present invention relates to a piezoelectric thin film element and a piezoelectric thin film device using a lithium potassium sodium niobate film, etc.
2. Description of Related Art
A piezoelectric material is processed into various piezoelectric elements in accordance with various purposes, and is widely utilized particularly as an actuator for adding voltage and generating deformation, and as functional electronic components such as a sensor that generates voltage from the deformation of an element reversely. As the piezoelectric material utilized for the purpose of the actuator and the sensor, a lead-based dielectric material having excellent piezoelectric characteristics, and particularly Pb(Zrx-1Tix)O3, which is particularly called PZT (described as PZT hereinafter)-based perovskite-type ferroelectric material has been widely used heretofore, and which is normally formed by sintering oxide composed of an individual element. Also, in recent years, development of the piezoelectric material not containing lead is desired, in consideration of an environment, and development of lithium potassium sodium niobate expressed by a general formula (NaxKyLiz)NbO3(0<X<1, 0<y<1, 0<z<1, x+y+z=1), etc, (called LKNN hereinafter), has been progressed. Such an LKNN has piezoelectric characteristics corresponding to PZT, and therefore is expected as a strong candidate. Note that LKNN includes a potassium sodium niobate film (KNN).
Meanwhile, at present, reduction in size and high performance of the piezoelectric element are strongly requested, while achieving the reduction in size and high performance of each kind of electronic component. However, regarding the piezoelectric material prepared by a sintering method-based manufacturing method, being a conventional manufacturing method, as its thickness is set to be thinner, and particularly as its thickness is set closer to a thickness of about 10 μm, the size of the piezoelectric material is closer to the size of a crystal grain constituting the material, and its influence can be hardly ignored. Therefore, there is a problem that variation of the characteristics and deterioration are remarkably generated, and in order to avoid such a problem, a forming method of the piezoelectric material, to which a thin film technique replacing the sintering method is applied, has been studied in recent years.
In recent years, a PZT thin film formed by RF sputtering is put to practical use as an actuator for a highly precise high speed inkjet printer head and a small-sized inexpensive gyro sensor (for example, see patent document 1 and non-patent document 1). Also, the piezoelectric thin film element using the piezoelectric thin film of LKNN not using lead is also proposed (for example, see patent document 2).